Does this test have other names?
What is this test?
This test measures how well your kidneys are working and how well blood is flowing
to them. Creatinine is a waste product that comes from normal muscle use and from
meat protein in your diet. Healthy kidneys remove creatinine from the blood. It then
passes out of your body through urine.
The creatinine clearance test usually compares the creatinine level in a 24-hour urine
sample with the creatinine level in your blood. This tells your doctor how well your
kidneys are working. Creatinine clearance also helps your doctor estimate your glomerular
filtration rate (GFR). This is the amount of blood cleaned by tiny kidney filters
called glomeruli each minute.
Why do I need this test?
You may need this test if you have symptoms that might be caused by kidney disease.
Signs and symptoms include:
Pain near the kidneys
Swelling or puffiness, especially around the eyes and ankles
High blood pressure
Low amount of urine or trouble urinating
Dark or foamy urine
Blood in the urine
Pain in the midback
You may also need this test if the results of other blood or urine tests suggest that
you may have a problem with your kidneys.
If you have already been diagnosed with kidney disease, your doctor can use this test
regularly to watch your kidney function and adjust your treatment if needed. If you
have diabetes, high blood pressure, congestive heart failure, or another disease that
affects the kidneys, you may have a creatinine clearance test to look for any changes
in your kidney function.
What other tests might I have along with this test?
You may also have a blood urea nitrogen (BUN) test. If your BUN level is high, it's
a sign that your kidneys may not be working as they should.
You may also have other tests to see how much protein is leaking from your kidneys
into your urine.
You may also have an ultrasound, CT scan, or other imaging test done of your kidneys.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Results are given in milliliters per minute (mL/min). The range for a normal test
result depends on your age and gender. For adults younger than 40, normal levels are
typically in the range of:
Creatinine clearance rates go down as you age. For every decade after age 40, a normal
test result is 6.5 mL/min less than the numbers above.
For newborns, the normal range is 40 to 65 mL/min.
An abnormal creatinine clearance rate may mean you have a problem with your kidneys.
Or it may mean a problem somewhere else in your body is affecting blood flow to the
How is this test done?
This test requires samples of blood and urine. The blood sample is drawn through a
needle from a vein in your arm.
For a 24-hour urine test, you must collect all of your urine for 24 hours. Empty your
bladder completely first thing in the morning without collecting it and note the time.
Then collect your urine every time you go to the bathroom over the next 24 hours.
This includes the following morning within 10 minutes of the time you collected your
first urine sample.
Follow your healthcare provider's instructions for storing the urine. Keep it out
of bright light and store it in a cool place, like the refrigerator.
Does this test pose any risks?
Giving a urine sample poses no known risks.
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
The 24-hour urine sample has to be exact. This means all urine must be collected and
properly stored during the test period. Otherwise the test results may not be accurate.
This is a common problem with the creatinine clearance test. Many doctors use a formula
based on your blood creatinine levels alone to estimate the GFR.
If you are pregnant or have recently done intense exercise, such as running a marathon,
your creatinine clearance rate could be higher than normal.
Certain medicines can cause creatinine clearance levels to be lower than normal. These
include cimetidine, procainamide, certain antibiotics, and quinidine. Certain conditions,
such as diabetes and congestive heart failure, may also affect the results.
How do I get ready for this test?
You don't need to prepare for this test. Be sure your doctor knows about all medicines,
herbs, vitamins, and supplements you are taking. This includes medicines that don't
need a prescription and any illicit drugs you may use.